1. Field of the Invention
The present invention relates to an antenna, and more particularly to a Plated Inverted-F Antenna (PIFA) applied to a MIMO wireless network device and a wireless network device having the same.
2. Description of the Prior Art
Referring now to FIG. 1, an outline perspective view of a traditional wireless network device 10 is illustrated. Generally, the wireless network device 10 is provided with a body 11, an internal circuit device 12 formed in the body 11, a connector 13 formed on a first end of the body 11 for connecting to an external host (not shown), and an antenna signal transmitter/receiver 14 formed on a second end of the body 11 opposite to the first end thereof. Broadly, the antenna signal transmitter/receiver 14 has an outer housing made of non-metal material. When the wireless network device 10 is connected to the external host, the antenna signal transmitter/receiver 14 must be exposed out of the external host in order to effectively receive and transmit wireless signals.
Referring now to FIG. 2, a schematic view of a traditional internal circuit device 20 of a MIMO wireless network device is illustrated. The internal circuit device 20 of the MIMO wireless network device is provided with a substrate 21, a control circuit 22 formed on the substrate 21, a ground portion 23 covered on a predetermined region of the substrate 21, and an antenna unit 24 electrically connected to the control circuit 22. The antenna design of wireless network device fit to MIMO specification is an antenna unit having three antennae for constituting three transmitters and two receivers. For example, the traditional antenna unit 24 shown in FIG. 2 is provided with a first antenna 241 formed on a middle portion thereof, a second antenna 242 formed on one side of the first antenna 241, and a third antenna 243 formed on the other side of the first antenna 241, all of which are adjacent to each other. The first antenna 241 is a T type dipole antenna extended toward the direction of an X axis shown in the right portion of FIG. 2. Furthermore, the second antenna 242 and the third antenna 243 are two monopole antennae disposed on two sides of the first antenna 241 and respectively extended toward the opposite direction of a Y axis shown in FIG. 2. Due to the antenna design of the traditional internal circuit device 20 as described above are selected from a printed antenna formed on the substrate 21, the second antenna 242 and the third antenna 243 are usually designed into different shapes for improving the radiation pattern and the gain value on an X-Y plane shown in FIG. 2, but the gain value on the vertical direction of a Z axis shown in FIG. 2 can not be improved at all. However, the present trend for designing wireless network devices is a vertical stand design for minimizing the occupied space of the wireless network devices, while enhancing the modern and high-technology appearance thereof. Apparently, the traditional printed antenna generates unwanted gain on the vertical direction of the Z axis, so that the traditional printed antenna can not satisfy the need of the vertical stand design of the wireless network devices.
For example, referring now to FIGS. 3 and 4, a detected radiation pattern on an X-Y plane of the second and third antennae 242,243 of the traditional MIMO antenna unit 24 shown in FIG. 2 is illustrated. As shown in the radiation pattern of FIGS. 3 and 4, the second antenna 242 has a maximum gain value on the vertical direction about −13.97 dBi, and the third antenna 243 has a maximum gain value on the vertical direction about −15.97 dBi. However, the maximum gain values are obviously lower than a lower limit value (generally, greater than about −10 dBi) which is set for satisfying consumers' acceptance, so that it is needed to improve the antennae design.
It is therefore tried by the inventor to develop an antenna and a wireless network device having the same to solve the problems existed in the traditional wireless network device as described above.